1. Field of the Invention
The present invention relates to a liquid discharge head for discharging liquid, and particularly to an ink jet recording head for recording by discharging ink onto a medium to be recorded.
2. Description of the Related Art
As an example of using a liquid discharge head for discharging liquid, there is an ink jet recording system for recording by discharging ink to a medium to be recorded.
Today, there are the following general ink discharge methods for use in the ink jet recording system: a method of using an electrothermal transducing element such as, for example, a heater as a discharge energy generating element for use in discharging ink droplets and a method of using, for example, a piezoelectric element. Both methods are capable of controlling the discharge of ink droplets by using electric signals.
The principle of the ink discharge method using the electrothermal transducing element is that a voltage is applied to the electrothermal transducing element to thereby bring the ink in the vicinity of the electrothermal transducing element to boil momentarily and bubbles rapidly grow owing to a phase change of the ink during the boiling to thereby discharge the ink droplets at a high speed. The ink discharge method using the electrothermal transducing element is advantageous in that there is no need to secure a large space for disposing the discharge energy generating element, the structure of the recording head is simple, and nozzles can be easily integrated.
In recent years, a desire for increasing the printing speed of color images is increasing more and more due to the speedup of processing speed of a personal computer and the spread of the Internet and digital cameras, which increases the demand for rapidly printing out a high-resolution document. Therefore, an ink jet head mounted on an ink jet printer is required to have a performance of discharging finer droplets and of providing a nozzle arrangement density of 300 dpi or more.
On the other hand, along with the decrease in size of droplets and the increase in recording density, the need for correcting a discharge state or the landing position of discharged droplets has been increased to thereby generate the need for adjusting a discharge angle into a nozzle arrangement direction. As a method of adjusting the discharge angle into a discharge port arrangement direction, there is a method of discharging droplets from a nozzle, which is oblique to a face surface of the discharge port, onto a substrate surface, as disclosed in Japanese Patent Laid-Open No. H02-198857. Furthermore, Japanese Patent Laid-Open No. H01-118443 discloses a method of adjusting a discharge angle by offsetting a discharge port with respect to a heater.
When there is a need to obtain an image having a high recording density as in recent years, however, it is often hard to form a nozzle capable of discharging liquid at a desired discharge angle in the method disclosed in Japanese Patent Laid-Open No. H02-198857.
On the other hand, in the technique disclosed in Japanese Patent Laid-Open No. H01-118443, the angle is adjusted in the supply port direction when viewed from the discharge port, which is perpendicular to the discharge port arrangement direction. If the angle is to be corrected into the discharge port arrangement direction using this method, there is a need to offset the discharge port into the discharge port arrangement direction with respect to the heater. In view of the information disclosed in Japanese Patent Laid-Open No. H01-118443, however, the problem below will occur. The effect on the discharge angle caused by offsetting the discharge port with respect to the heater decreases as the discharge aperture is reduced. Therefore, a very large offset amount is required in comparison with the conventional one to achieve a desired discharge angle when using a discharge port having a fine aperture as needed in recent years. Therefore, it is very hard to design a nozzle having such an offset amount under the condition of the 300 dpi or higher nozzle arrangement density. Furthermore, if the nozzle is designed so as to have the required offset by decreasing the nozzle arrangement density, it causes a problem that discharge efficiency drops because of an increase in the distance from a heater to a flow path wall in the offset direction.
As described hereinabove, conventionally there has not been a satisfactory method of adjusting a discharge angle of discharged droplets into a discharge port arrangement direction without decreasing the discharge efficiency in an ink jet head having a high nozzle arrangement density with a discharge port having a fine aperture.